I reviewed a NestJS fintech backend where the numbers never quite matched, this is the fix

I was asked to look at a fintech backend where something small but persistent kept happening. Every month when the finance team tried to close the books, the internal ledger and the payment processor's own records were off by a small amount. Not a dramatic amount, sometimes a few transactions, ...

Source: [Dev.to](https://dev.to/peacemelodi/i-reviewed-a-nestjs-fintech-backend-where-the-numbers-never-quite-matched-this-is-the-fix-237i)